Transport properties of proton-irradiated gallium nitride-based two-dimensional electron-gas system

A two-dimensional electron gas system (2DEG) is formed at the interface when a ternary alloy of aluminum gallium nitride is grown on gallium nitride. Very high carrier density can be achieved in these systems due to the strong piezoelectric and pyroelectric properties of the nitrides. The device was grown by molecular beam epitaxy and magnetron sputtering epitaxy. Through resistivity and Hall effect measurements in the temperature range 2 K to 300 K, its 2DEG conductive character, high mobility, and carrier density properties were confirmed. The effects of 2-MeV proton radiation on these properties are reported for the fluence range 1 × 10¹³ to 7 × 10¹⁵ cm^-2. As a result of irradiation, the carrier density decreases by a factor of two whereas the mobility degrades by about a factor of a thousand. A fluence between 3 × 10¹⁴ cm^-2 and 3 × 10¹⁵ cm^-2 is necessary to drive a conductor to insulator transition for this 2-D gas and the change of phase is attributed mainly to changes in the mobility. This change of phase is determined by quantum conditions and could be used to establish an absolute standard for radiation damage.